In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that area from the solenoid to the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are spaced in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower print head to be used and thereby reduces the width of the printer because of the reduced clearance required at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer, the print head structure may be a multiple-element type with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner, while the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally-aligned single-element print heads which are caused to be moved in back-and-forth manner to print successive lines of dots in making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing. These single wire actuators or solenoids are generally tubular or cylindrically shaped and include a shell which encloses a coil, an armature and a resilient member arranged in manner and form wherein the actuator is operable to cause the print wire to be axially moved a small precise distance in dot matrix printing.
In the concept of dot matrix printing, it is generally desired to place the print element actuators in a position to allow characters to be printed in serial manner and this placement requires that the print wire or like print element actuators be very closely spaced with respect to each other. Since the print actuators are generally much larger in size than the diameter of the printed dot, a relatively long wire or like element must be provided to bring the desired print activity from its source, such as a moving armature or plunger or the like, to a vertical closely-spaced column arranged in a pattern such that the column of closely-spaced, tangentially-coincident dots will be produced on the record media if all actuators are fired or actuated at one time.
Representative documentation in the field of wire matrix print heads includes U.S. Pat. No. 3,994,381, issued to D. G. Hebert on Nov. 30, 1976, which discloses a wire matrix print head having a plurality of print wires with input ends arranged in an elliptical format and supported and guided at several points by means providing for a minimal amount of bending along the length of the wires.
U.S. Pat. No. 4,051,941, issued to D. G. Hebert on Oct. 4, 1977, discloses a matrix print head with guide means at several points for the print wires which are operably associated with armatures actuated by electromagnetic structures.
U.S. Pat. No. 4,185,929, issued to D. G. Hebert on Jan. 29, 1980, discloses a print head assembly with relatively long length and short length bearing and guide members to provide continuous wire passage and to enable uninterrupted slidable insertion of the print wires during assembly.
U.S. Pat. No. 4,230,038, issued to D. G. Hebert on Oct. 28, 1980, discloses a print head assembly having a housing of molded plastic with print wire guide and support means of axially-spaced plate members at several points and with apertures for containing the wires in an elongated path.
U.S. Pat. No. 4,230,412, issued to D. G. Hebert on Oct. 28, 1980, discloses a print head assembly having an elongated wire guide and support portion and an annular housing portion along with a cover portion for the armature members.
And, U.S. Pat. No. 4,279,518, issued to J. E. Blomquist et al. on July 21, 1981, discloses a dot matrix print head with a single unit coil assembly which can be removably placed as a unit among pole pieces and yoke members, along with a supporting arrangement which automatically aligns the clapper of each coil assembly with the impact end of a print wire. Also disclosed are novel assembly aids and procedures which simplify and hasten the assembly of the print head and including the use of assembly aids for inserting the print wires into the several wire guide members.